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UBUNTU-CVE-2021-33909
Vulnerability in linux (UBUNTU-CVE-2021-33909)
Summary
vulnerability in linux (UBUNTU-CVE-2021-33909). Successful exploitation can lead to full system takeover. Mitigation: upgrade to `3.13.0-186.237` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **UBUNTU-CVE-2021-33909** has been found in linux.
Successful exploitation can lead to full system takeover. CVSS score: ?/10.
What to do: upgrade linux to **3.13.0-186.237** or later.
If unsure, ask your IT team or search "linux UBUNTU-CVE-2021-33909" on the vendor's site.
UBUNTU-CVE-2021-33909 (linux) —
Attack vector: local / no user interaction
Patched: `3.13.0-186.237` — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
❓ What is the problem
**A vulnerability** (unclassified) exists in linux.
📍 Affected scope
linux — .
🔥 Severity
Severity: ?. Successful exploitation can lead to full system takeover
🔧 How to fix
Update to **3.13.0-186.237**.
🛡️ Workaround
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
🔍 Detection
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run `grep -r 'linux' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response Actions (7 steps)
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'linux' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で `linux` を grep し、稼働しているサービス・バージョンを把握する。
-
6Apply patch patch
Upgrade linux to 3.13.0-186.237ステージング環境で 3.13.0-186.237 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 3 で見つけた異常検知の続報チェックを含めること。
-
7Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 3 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
Ubuntu:Pro:14.04:LTS
linux
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.13.0-186.237"}]}]
Ubuntu:Pro:14.04:LTS
linux-aws
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.4.0-1094.99"}]}]
Ubuntu:Pro:14.04:LTS
linux-azure
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1121.134~14.04.1"}]}]
Ubuntu:Pro:14.04:LTS
linux-lts-xenial
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.4.0-212.244~14.04.1"}]}]
Ubuntu:Pro:16.04:LTS
linux
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.4.0-212.244"}]}]
Ubuntu:Pro:16.04:LTS
linux-aws
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.4.0-1130.144"}]}]
Ubuntu:Pro:16.04:LTS
linux-aws-hwe
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1109.116~16.04.1"}]}]
Ubuntu:Pro:16.04:LTS
linux-azure
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1121.134~16.04.1"}]}]
Ubuntu:Pro:16.04:LTS
linux-gcp
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1106.120~16.04.1"}]}]
Ubuntu:Pro:16.04:LTS
linux-hwe
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-151.157~16.04.1"}]}]
Ubuntu:16.04:LTS
linux-hwe-edge
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:16.04:LTS
linux-kvm
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.4.0-1095.104"}]}]
Ubuntu:Pro:16.04:LTS
linux-oracle
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1078.86~16.04.1"}]}]
Ubuntu:Pro:FIPS:16.04:LTS
linux-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-151.157"}]}]
Ubuntu:18.04:LTS
linux-aws
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1109.116"}]}]
Ubuntu:18.04:LTS
linux-aws-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1054.57~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-azure-4.15
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1121.134"}]}]
Ubuntu:18.04:LTS
linux-azure-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1055.57~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-dell300x
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1027.32"}]}]
Ubuntu:18.04:LTS
linux-gcp-4.15
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1106.120"}]}]
Ubuntu:18.04:LTS
linux-gcp-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1049.53~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-gke-5.3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.3.0-1045.48"}]}]
Ubuntu:18.04:LTS
linux-gke-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1049.52~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-gkeop-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1021.22~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-hwe
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.3.0-76.72"}]}]
Ubuntu:18.04:LTS
linux-hwe-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-80.90~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-kvm
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1097.99"}]}]
Ubuntu:18.04:LTS
linux-oracle
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1078.86"}]}]
Ubuntu:18.04:LTS
linux-oracle-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1052.56~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-raspi-5.4
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1041.45~18.04.1"}]}]
Ubuntu:18.04:LTS
linux-raspi2
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1092.98"}]}]
Ubuntu:18.04:LTS
linux-raspi2-5.3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.3.0-1042.44"}]}]
Ubuntu:18.04:LTS
linux-snapdragon
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1109.118"}]}]
Ubuntu:18.04:LTS
linux-aws-5.0
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-aws-5.3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-azure
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-azure-5.3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-azure-edge
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-gcp
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-gcp-5.3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-gcp-edge
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-gke-4.15
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-hwe-edge
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-oem
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-oracle-5.0
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:18.04:LTS
linux-oracle-5.3
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS-updates:18.04:LTS
linux-aws-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-2051.53"}]}]
Ubuntu:Pro:FIPS-updates:18.04:LTS
linux-azure-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-2033.37"}]}]
Ubuntu:Pro:FIPS-updates:18.04:LTS
linux-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-1066.75"}]}]
Ubuntu:Pro:FIPS-updates:18.04:LTS
linux-gcp-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.15.0-2016.18"}]}]
Ubuntu:Pro:FIPS:18.04:LTS
linux-aws-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS:18.04:LTS
linux-azure-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS:18.04:LTS
linux-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS:18.04:LTS
linux-gcp-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:20.04:LTS
linux
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-80.90"}]}]
Ubuntu:20.04:LTS
linux-aws
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1054.57"}]}]
Ubuntu:20.04:LTS
linux-aws-5.11
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.11.0-1014.15~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-aws-5.8
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.8.0-1041.43~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-azure
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1055.57"}]}]
Ubuntu:20.04:LTS
linux-azure-5.11
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.11.0-1012.13~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-azure-5.8
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.8.0-1039.42~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-bluefield
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1016.19"}]}]
Ubuntu:20.04:LTS
linux-gcp
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1049.53"}]}]
Ubuntu:20.04:LTS
linux-gcp-5.11
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.11.0-1014.16~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-gcp-5.8
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.8.0-1038.40~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-gke
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1049.52"}]}]
Ubuntu:20.04:LTS
linux-gkeop
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1021.22"}]}]
Ubuntu:20.04:LTS
linux-hwe-5.11
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.11.0-25.27~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-hwe-5.8
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.8.0-63.71~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-kvm
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1044.46"}]}]
Ubuntu:20.04:LTS
linux-oem-5.10
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.0-1038.40"}]}]
Ubuntu:20.04:LTS
linux-oracle
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1052.56"}]}]
Ubuntu:20.04:LTS
linux-oracle-5.11
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.11.0-1013.14~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-oracle-5.8
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.8.0-1037.38~20.04.1"}]}]
Ubuntu:20.04:LTS
linux-raspi
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1041.45"}]}]
Ubuntu:20.04:LTS
linux-oem-5.6
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:20.04:LTS
linux-raspi2
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:20.04:LTS
linux-riscv
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:20.04:LTS
linux-riscv-5.8
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS-updates:20.04:LTS
linux-aws-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1069.73+fips2"}]}]
Ubuntu:Pro:FIPS-updates:20.04:LTS
linux-azure-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1073.76+fips1"}]}]
Ubuntu:Pro:FIPS-updates:20.04:LTS
linux-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1031.36"}]}]
Ubuntu:Pro:FIPS-updates:20.04:LTS
linux-gcp-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.4.0-1067.71~20.04.1"}]}]
Ubuntu:Pro:FIPS:20.04:LTS
linux-aws-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS:20.04:LTS
linux-azure-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS:20.04:LTS
linux-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:FIPS:20.04:LTS
linux-gcp-fips
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:22.04:LTS
linux-intel-iot-realtime
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:22.04:LTS
linux-realtime
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:24.04:LTS
linux-raspi-realtime
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:26.04
linux-nvidia
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
References
- advisory https://ubuntu.com/security/notices/USN-5018-1
- advisory https://ubuntu.com/security/notices/USN-5017-1
- advisory https://ubuntu.com/security/notices/USN-5016-1
- advisory https://ubuntu.com/security/notices/USN-5015-1
- advisory https://ubuntu.com/security/notices/USN-5014-1
- report https://ubuntu.com/security/CVE-2021-33909
- report https://www.qualys.com/2021/07/20/cve-2021-33909/sequoia-local-privilege-escalation-linux.txt
- report https://www.openwall.com/lists/oss-security/2021/07/20/1
- report https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b
- report https://www.cve.org/CVERecord?id=CVE-2021-33909